I wouldn't want a 16 year old dispatching my train !
Everyone on the railway is a railwayman, if they clean the bogs or are the head of a TOC, never, ever look down on anyone else's job on the railway because with one balls up, you can very soon find yourself doing that job you looked down on, alongside the person to whom you displayed a superior attitude !
If you are 16 and want a railway job, go for it, try it, but remember if you get one, you can kiss your ass goodbye to all the things that I would have hated to have missed at 16-20 such as wild nights out, house party and university orgies etc., etc., etc., !
What you will get as a railway job at 16 is very limited in scope though, so you will have to take what you get and look across the entire railway spectrum.
If you REALLY, REALLY want a railway job at the earliest possible age, then my plan, If I were you would be :
Get a retail or warehouse job now, Join the RAF, the Navy or the Army as soon as you can when you reach recruitment age, spend 3 years doing that gaining as many trade skills as possible
Then start applying for railway jobs